The organic Rankine cycle (ORC) is a Rankine cycle that employs an organic fluid as working medium to generate power from lower temperature sources such as biomass combustion, industrial waste heat, and geothermal heat [1–5].

Some of the wasted heat may be recovered using the Rankine cycle, where an intermediate heat transfer loop is added that contains a working fluid whose properties allow it to pass through an expander to capture some of the exergy of the waste heat sources.

The working principle of the organic Rankine cycle is the same as that of the Rankine cycle: the working fluid is pumped to a boiler where it is evaporated, passed through an expansion device (turbine, screw, scroll, or other expander), and then through a condenser heat exchanger where it is finally re-condensed.

ORC systems are based on similar principles to steam turbines but use organic silicon oil as the operating medium, rather than water or steam. Organic oils employ lower temperatures and pressures compared with steam-based systems.